Welcome to Forgotten Cars, where we highlight fascinating cars and engines that are obscure, unrecognized and lost to the passage of time.

With Holden having released the first shots of their new Commodore last night, I thought it only fitting that today's Forgotten Cars entry come from Australia's RWD-loving division of General Motors. This, however, is a car that they would probably rather everyone forget about.

Well, look at that. General Motors' Australian subsidiary Holden dropped the first photos of…
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Meet the Mazda Roadpacer. What you see here is a giant Holden sedan with all the trappings you'd expect from a huge GM car from the 1970s. But what's under that long hood is what makes it unique: a Mazda rotary engine. No, it's not some one-off engine swap thing, it's for real, and it was actually sold in Japan from 1975 to 1977 before the plug was pulled.

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I think this car is neat because it combines three things I really like: big Aussie cars, rotary engines, and captive imports. In reality, however, it was terrible.

Have you ever noticed that the term "import car" doesn't get tossed around like it…
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Here's how this broke down: In the 1970s, Mazda was a plucky, small Japanese automaker with big dreams. They wanted to expand their lineup by adding a full-size car, but they didn't have the platform for it. Enter GM, who wanted information from Mazda on rotary engines, possibly for one of the aborted mid-engine rotary Corvette attempts from that era, according to Mazda Rotary Enthusiasts Club New Zealand.

So here's the deal they worked out. GM would ship their Holden HJ Premier sedans to Japan without an engine. Mazda would put in their 1.3-liter 13B rotary engine. The resulting car (complete with ridiculous JDM hood-mounted side mirrors) was off to pace the roads under the name Mazda Roadpacer.

The car had a few other curious features. It included a fridge in the trunk as well as a Dictaphone, according to Hooniverse. I'm not sure who the target market was, but I can see this thing being popular among journalists in the 1970s. You could do interviews in the car and even feed your source some snacks from the fridge. Brilliant!

Unfortunately, there was a big problem: power. This was a far cry from the twin-turbo rotaries that would humiliate lesser cars on the track in two decades. The naturally-aspirated 13B put out a decent 130 horsepower, about on par with the Holden's previous straight-six, but at a lofty 6,000 RPM. And with a meager 102 pound-feet of torque, it struggled to move the 3,470-lb. Roadpacer anywhere. Oh, and it got 10 miles per gallon and was ridiculously expensive for its time. Put all of these things together and you have a car that was basically awful to drive.

Frankly, I just can't see why no one figured out this was a terrible idea. Rotary engines have a lot of advantages, like fewer moving parts, light weight, and ridiculously high RPM limits. But they tend to be not so great on gas, emissions, and low-end torque. So why on Earth did anyone think it was a good fit for a big car like the Holden?

Listen people, this is Performance Car 101: You put the BIGGER engine into the SMALLER car. This is a very simple concept! GM, you of all people should have known this; you did muscle cars for decades, and when you get down to brass tacks, that's really all a muscle car is. Or maybe you did know better and you hosed poor little Mazda. They definitely got the short end of the stick here.

Only about 800 Roadpacers were ever sold before the car was canceled, and it became the butt of many jokes in the Japanese auto industry. And today, it remains the only production GM car to ever have a rotary engine.